. . . . . . "6 Pt 1" . "1998-2-9" . "Regulation of phosphatidylinositol (PI) 3-kinase plays an important role in modulating cellular function. We have previously shown that transforming growth factor (TGF)-beta 1 inhibited epidermal growth factor (EGF)-induced human airway smooth muscle (hASM) cell proliferation and that PI 3-kinase activation is a necessary signaling event in mitogen-induced hASM cell growth. In this study, we postulated that TGF-beta 1 may modulate EGF-induced PI 3-kinase activation. To date, no study has examined the effects of TGF-beta 1 on PI 3-kinase activity. In cultured hASM cells, EGF induced a 5.7 +/- 1.2-fold activation of PI 3-kinase compared with diluent-treated cells. Although TGF-beta 1 alone did not alter PI 3-kinase activation, TGF-beta 1 markedly enhanced EGF-induced PI 3-kinase activity, with a 16.6 +/- 1.9-fold increase over control cells treated with diluent alone. EGF significantly increased the association of PI 3-kinase with tyrosine phosphorylated proteins, and TGF-beta 1 pretreatment before EGF stimulation apparently did not alter this association. Interestingly, TGF-beta 1 did not modulate EGF-induced p70 S6 kinase activity, which is important for the progression of cells from the G0 to the G1 phase of the cell cycle. Immunoprecipitation of type I and type II TGF-beta receptors showed that PI 3-kinase was associated with both type I and type II TGF-beta receptors. TGF-beta 1, however, enhanced PI 3-kinase activity associated with the type I TGF-beta receptor. Although in some cell types inhibition of PI 3-kinase and treatment of cells with TGF-beta 1 mediate apoptosis, cell cycle analysis and DNA ladder studies show that PI 3-kinase inhibition or stimulation of hASM cells with TGF-beta 1 did not induce myocyte apoptosis. Although the inhibitory effects of TGF-beta 1 on hASM cell growth are not mediated at the level of PI 3-kinase and p70 S6 kinase, we now show that activation of the TGF-beta 1 receptor modulates PI 3-kinase activity stimulated by growth factors in hASM cells." . . "eng" . . "IM" . . . . . . . "MEDLINE" . "Dec" . "0002-9513" . . . . . . "Print" . "273" . "NLM" . "Y" . "L1220-7" . "2010-11-18" . . . . . . . . . . . . . . "1997" . "TGF-beta 1 modulates EGF-stimulated phosphatidylinositol 3-kinase activity in human airway smooth muscle cells." . "Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia 19104, USA." . "Journal Article" . "Research Support, U.S. Gov't, P.H.S." . "Research Support, U.S. Gov't, Non-P.H.S." . "Research Support, Non-U.S. Gov't" .